Final answer:
The correct answer to how Biosphere 2 could be modified into an open system is by d) removing the glass enclosing the structure. This action would allow the internal closed ecosystems to exchange matter and energy with the external environment.
Step-by-step explanation:
The student's question is regarding how Biosphere 2 could be transformed into an open system. In ecological science, a system is considered open if it exchanges energy and matter with its surroundings. An example of an open system is Earth's biosphere, while a closed system, like Biosphere 2, is designed not to exchange matter with the outside environment. In the context of Biosphere 2, turning it into an open system would require allowing the exchange of matter and energy with the external environment.
Of the options provided, removing the glass enclosure that surrounds the structure would effectively turn the biosphere into an open system. The glass enclosure functions to separate the internal environment from the external world, thereby preventing the free exchange of materials and energy. By removing the enclosure, the ecosystems inside Biosphere 2 would be subject to external conditions such as atmospheric gases and climate, thus becoming part of the larger Earth biosphere. Therefore, the correct option is (d) removing the glass enclosing the structure.
It should be noted that the other options provided would not make the system open. Removing microbes from the soil or adding more oxygen gas would still keep the system closed as it does not facilitate exchange with the external environment. Blocking sunlight would not open the system either; it would only limit the energy input to the ecosystems within Biosphere 2.